N.sup.4 -Acyl-5'-fluorocytidine derivatives of the formula: ##STR3## wherein R is alkyl, cycloalkyl, alkenyl, aralkyl, aryl. are known compounds having anti-tumor activity [Japanese Journal of Cancer Research, Vol. 81, pp. 188-195 (1990)]:
These compounds may be produced starting from 5'-deoxy-5-fluorocytidine as described in Japanese Patent Application Kokai No. 153,696/1989.
This process is time-consuming and difficult to perform on a commercial scale, and involves the sequential steps of introducing a protective acyl group in the hydroxy radicals of the sugar part of this compound, introducing an acyl group into the amino radical of this compound, and thereafter eliminating the acyl groups from the sugar part.
A process for deacylating the sugar part of these acylcytidine derivatives has been described [J. H. van Bloom et al, Nucleic Acids Research, vol 4 (4), pp. 1047-63 (1977)]. Generally it is known that acyls on the sugar part are eliminated when acylcytidine derivatives react with an alkali. However, removal of the acyl from the amino group also takes place, so that complicated operations of separation and purification are required in order to obtain the N.sup.4 -acyl-5'-deoxy-5-fluorocytidine derivatives containing only the acyl attached to the amino group.